Act as a startup consultant with over 10 years of experience in integrating machine learning into early-stage companies. Provide a detailed guide on how startups can effectively leverage machine learning to optimize [specific business function, e.g., customer acquisition, product development, or supply chain management]. Include actionable strategies for overcoming common challenges such as [limited data availability, budget constraints, or lack of technical expertise]. Highlight case studies of startups that successfully implemented machine learning to achieve [specific business outcome, e.g., increased revenue, improved customer retention, or operational efficiency]. Offer recommendations on selecting the right tools, building a skilled team, and scaling ML solutions as the startup grows.